Method and apparatus for controlling projection of light by sound waves



June 13, 1933.. R. v. WOOD 1,913,867

, METHOD AND APPARATUS FOR CONTROLLING PROJECTION OF LIGHT BY SOUND WAVES Filed Jan. 29, 1952 INVENTOK flevzs'en/fu ood I425 ATTORNEY- specification.

v and adjusting a lig Patented June 13, 1933 BEMSENT. WOOD, OF ROCHESTER, NEW YORK METHOD AND APPARATUS FOR CONTROLLING PROJECTION OF LIGHT BY SOUND WAVES a uaaon filed January as, 1932. Serial No. saasso.

This invention relates to methods and aparatus for controlling the projection of light y means of sound waves, one object of the invention being-to provide a method and ap- 5 paratus for this purpose of a more simple,

to control the pro ection of light on a sensitive material, such, for example, as a motion 15 picture or other photographic film A still further object is to provi recording method and apparatus utlhzlng the efiect of interfering li ht waves produced by the sound to be recor ed.

To these and other ends, the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel features being pointed out in the claims atathe end In the drawing:

Fig. 1 is a general view, partly diagrammatic andpartly in section, showing an apparatus for carrying out the method of the prelsent invention. and embodying the same,

Fig. 2 is a view of a portion of the apparatu's taken at right angles toFi .1 and more particularly showingl t reflecting means em-.

plolyed in the invention.

he samer'eference numerals throughout I row. slit aperture, as well understood inthe the several views indicate the same parts.

- The invention is disclosedherein, by way 40 of illustration, as applied to the'use of record- -in sound on a. motion picture film, but it wi lbexundei'stood, of. course, that'its princi n ples may be adapted and applied to other uses.

-One?aspect of the invention provides a methodfor' controlling the projection .of

' light by means of sound waves. For this purpose a'very thin, flexible, .tfjgmsparentdia phragm is formed of suitablel'inaterial, such, for example, as cellulose nitrate-or other cele provision of a. more.

do a sound of the a means or mounting lulosic material capable of being prepared, in known ways, to produce such a diaphragm. This diaphragm is then stretchedover a support or frame so that it ma be set into vi-' bration by sound wave impu ses;

A beam of light from a suitable common source is projected at'an acute angle against the diaphragm with the result that a portion of the beam is reflected, while another portion is refracted or transmitted through the diaphragm and projected at its opposite side. The angle of incidence of the original beam is preferably such that the said reflected and re racted portions are substantially equal'in intensity. .The portion reflected from the diaphragm is again reflected back toward the point of incidence by any suitable means, such as a mirror, so that a part at least of this reflected portion of the beam is then refracted and transmitted through the diaphragm and projected at its opposite side; The other portion of the original beam which is refracted through the diaphragm is likewise reflected back toward the point of refraction by' any suitable means, such as a mirror, with the result that a part at least of this beam is then reflected from the opposite side of the diaphragm and projected at such opposite side. The two reflectin means or mirrors located on opposite-Si es of the dia- 0 ,phra'gm are so ad usted that the two beam art, and with any suitable collimating lens means, and also with '3, color filter if so desired. Objective lens vmeans are also provid- "ed in the path of the rays reflected and superposed as described at'the opposite side of the film, for the pur ose of collecting or condensing the same to orm, on a motion picture film 'or other; receiving surface, superposed images of the aperture slit.

It is apparent thatv by directing sound waves against-the thin film or diaphra it may be set intovibratory motion an' that 9 ing out the above method is illustrated in the these reflected beams of less than a wave.

the vibrations will difierentially vary the lengths of the beams reflected from its oppositesides and thence superposed by the mirrors. Such vibrations of the diaphragm thus produce diflerences between the lengths of it can be reproduced by known or suitable sound re reducing devices, as well unders in t e art.

One [form of apparatus suitable for carrydrawing, partly in a diagrammatic manner for the purpose of avoidingunnecessary de-' tail. This apparatus preferablycomprises a base plate 5 having therein a circular central o nmg 6 about which, on one side of the p ate, is a circular shoulder or bridge 7 over which the said thin, flexible trans arent diaphragm 8.is stretched. The perip eral edges vof the diaphragm are preferably cemented I between rubber rings 9, for securely holding and mounting the diaphragm with the least danger of injury. These rings 9 are held on the base plate 5 by means of an annumeans of the diaphragm.

Q 6 dia hra are thus located at a height slightlar plate 10 through which screws 11 are passed into the plate 5 and by means of which the plate 10 is drawn down in clamping engagement with. the peri heral mounting s the edges of the \ly ess 51 51 11 that of the bridge 7, the result is to stretch the diaphragm taut over the bridge 7 and across the opening 6.

A suitable light source is indicated conventionally at 12 and may be provided with a color filter 13 of any known or suitable variety. The light source is also provided with a partition or plate 14 having formed therein a slit aperture 15 of narrow, width, say

' 0.003 inches. The beam of light projected "from the source through this slit aperture passes through suitable collimatinglens means indicated diagrammatically at 16 from which parallel rays are projected through the 0 ening 6 of plate 5-and against the'center 0? the diaphragm 8. It is evident that portions of this incident beam will be respectivelyreflected from the surface or surfaces of the diaphragm and also refracted or transmitted through the same to its opposite side. It is preferred,' as stated above, toselect such amass? an angle of incidence of the beam from the light source on the that these reflected and refracted portions of the beam will hav about the same intensity.

A portion of the beam reflected from the diaphragm is indicated at 17 and a suitable means or reflector, such as the mirror 18, is provided for reflecting this beam portion back toward the point of incidence so that a part at least of the beam 17 is refracted and transmitted through the diaphragm and projected at its opposite side as indicated at 19.

The portion of the beam from the light source which is refracted or transmitted through the diaphragm is indicated at 20 and a suitable means or' reflector, such as the mirror 21, is provided and positioned to reflect this beam portion back toward the point of refraction by the diaphragmso that a portion at least is reflected by the diaphragm as indicated at 22 at the opposite side of the film.

The reflectors or mirrors 18 and 21 are so disposed as to cause the beams 19 and 22 to form superposed slit images at a common point 23 on a sensitive material such, for example, as the motion picturefilm 24, suitable objective lens means, as indicated at 25, 'bein rovided for this prpose as well understood 1n the art.

, Suitable means are provided for effecting relative adjustment between the reflecting mirrors 18 and 21 in order to superpose the reflected images. Such adjusting means may obviously have different forms and in the present instance the mirror 18 has fixed thereto a clip 26 secured by means of ascrew to the plate 5 in the desired position. Mirror 21 is fixed on a clip 27 secured by means of a screw to a plate rame or spider 28 having three main arms 29, 30 and 31 fixed ,by means of screws to supporting posts 32, 33 and 34 rising to an equal height from the plate 5. The latter is provided also with spaced posts 35 and 36 on opposite sides of the s ider and terminating at' some distance elow it. Spider arms 37 and 38 extend over these shorter posts and carry screws 39 and 40, turning freely in the spider arms but threadedly engaged in openings in the tops of the corresponding posts, so that by turning either. or both of'these screws the spider plate may be warped to effect-the desired positioning of mirror 21 to cause the slit image reflected thereby to coincide with the image projected by the other mirror 18 at the common point 23.

Suitable means are provided for collecting and directing sound waves against the- ,vibratory diaphragm 8, as indicated in the It is evident from the above description that the sound waves impinging upon the amass? very thin and sensitive diaphragm 8, set up in the latter responsive and proportional vibrations which in turn produce a difierential variation between the lengths of the beams i? and 20 and the reflections thereof from the mirrors l8 and 21, with the result that known interference efiects are produced and made apparent in the intensity of the composite ima' e produced at 23, so that the in tensity or t is composite image varies inproportion to the intensity and volume of the sound directed against the diaphragm.

'lihe above method and apparatus thus combine in a simplc compact and unitary way several operations or functions heretofore commonly requiring several difierent units such, for example, as the micro hone, amplifier and light valve employed in nown apparatus for recording sound on a film. In view of the comparatively simple and direct manner in which such operations are accomplished, the present method and apparatus afi'ord advantageous simplicity of control and reliability and acc'uracy'in results, together with simplicity and economy in the apparatus required.

ll claim: I 1;. An apparatus for controlling light by sound comprising a light source, a transparent diaphragm arranged to vibratein response to sound waves, and means whereby the light from said source is transmitted through and reflected from opposite sides of said diaphragm and superposed, so that the vibration of said diaphragm tends to produce interfering light effects.

2. An apparatus for controlling light by sound comprising a light source, spaced reflectors, and a transparent diaphra m between said refiectors for reflecting amftrans mitting light from said source to and from said reflectors and to a common point, said diaphragm being arranged to vibrate in response to sound waves and to produce an in terference efiect apparent at said common point.

3. An apparatus for controlling light by sound comprising a light source provided reflected light is projected at said common point for producing a record on material by interference efiects.

5. A sound-recording apparatus compris ing alight source provided with a partition havingv a slit with a'collimating lens means, spaced reflectors, a flexibie transparent dia phragm between said reflectors for reflecting and transmitting lightfrom said slit to and from said reflectors and forming superposed slit images, and a sensitive material on which said slit images are projected for forming a record by interfering light wave efiects,

6, A method of recording sound comprising projecting light from a common source against one side of a thin flexible transarent film to cause said light to be refiecte by the surface of said film and also retracted through its opposite side, reflecting'said reflected' and refracted li ht back against the opposite sides of said I ha so that the light rays reflected from opposite sides of said film are superposed at a common point, locating a; sensitive material to receive said light rays at said common point and vibrating said film by sound waves to produce a record thereof on said material by interfering light wave efiects. i I

7. A method of recording sound comprisingprojecting light from a common source agalnstone side of a thin flexible trans ar-- ent film to cause said light to be reflecte by the surface of said vfilm and also refracted through its opposite side, reflecting said rereflected and refracted light back against the opposite sides of'said film to retract and refleet the light rays and superpose them at a:

common point, locating a recording means to receive. said light rays at said common point, and vibrating said film by sound waves to produce a record therof on said means by interfering light wave efiects.

' "REMSEN V. W003).

with a partition having an aperture and colli- Y mating lens means, spaced reflectors, and a flexible transparent diaphragm between said reflectors for refle'ct'ingand transmitting li ht from said aperture to and from said re ectors and forming superposed images of said aperture, said diaphragm being arranged to vibrate in response to sound waves an pro duce interference efii'ects in said images.

4. A sound recording apparatus comprisa li ht source, spaced reflectors, a transparent aphragm between said reflectors for reflecting and transmitting light from "said source to and from said reflectors and to a common point, said diaphragm being? arranged to vibrate in response to sound waves,

' 05 and a light sensitive material on which said 

